【作者】 武亚军；

【导师】 栾茂田；

【作者基本信息】 大连理工大学 ， 水工结构工程， 2003， 博士

【摘要】 在基坑工程中，土与支护结构相互作用、土的物理非线性与界面的接触非线性所构成的土工双重非线性和基坑边坡的稳定性是深基坑工程中的三个非常重要而基本的实际问题，一直得到了广泛的重视，但是目前尚未得到彻底的解决。为此本文针对这三个问题，分别开展了深入的探索，主要研究工作包括： 1．对于土与结构间接触面的切向本构关系，目前通常采用双曲线非线性弹性模型或刚塑性模型来描述，但是，传统的双曲线非线性模型不能明确地表达剪切破坏后的塑性流动变形特性；而刚塑性模型又无法描述剪切破坏之前的非线性弹性变形。对此，本文将非线性弹性理论与弹塑性理论相结合，提出了一种非线性弹性—理想塑性模型，剪切破坏之前所发生的剪切变形与剪切破坏之后的错动变形分别由非线性模型和刚塑性模型计算，这种混合模型能够比较全面地反映接触面的变形特性与破坏机理，以此为基础发展了用于模拟土与结构接触面特性的接触带单元。从计算角度，接触面的计算力学模型可以分为无厚度的接触面单元和有厚度的接触带单元，通过比较分析认为有厚度的接触带单元能够比较合理地描述土与结构的相互作用特性。 2．对于实际岩土工程中大量存在的土的物理非线性和土与结构间接触面的接触非线性这类双重非线性问题，本文将土的理想弹塑性模型和针对接触面所建立的非线性弹性—理想塑性本构模型相结合，发展了一套非线性数值解法，从而对于土工双重非线性问题提出了一种一套比较协调的计算模型与数值分析方法，并将其应用于深基坑支护与开挖及稳定性分析，实际计算表明这套方法是行之有效的。 3．针对目前边坡稳定性分析中常用的强度折减弹塑性有限元法所存在的失稳指标和失稳判断不明确等问题，本文提出了将广义塑性应变作为一种新的失稳指标，并依据广义塑性应变分布区的产生、发展乃至相互连通进行边坡稳定性的评判。本文通过对有限元计算结果的计算机实时显示技术全面实现了这种评判过程，即通过对图形实时显示的计算结果的观察，分析强度折减过程中广义塑性应变的发展变化，进而评判边坡的稳定性，多个算例的计算与分析表明不仅对于基坑边坡，而且对于实际工程中的天然边坡和人工切坡，这种稳定性分析方法是合理有效的。 4．采用Visual C++编写了面向对象的计算程序，实现了非线性—理想塑性接触面模型，实现了土工双重非线性问题的弹塑性有限元数值计算和以此为基础的边坡稳定性数值分析。该计算系统不仅具有较强的计算功能，而且拥有较强的前前后处理功能，在后处理中，有限元计算结果可以用等值线与彩色云图两种方法表达。结合基坑开挖与支护这样的变体系施工力学问题，将非线性有限元计算过程与实时显示技术相结合，随时通过图形显示了解施工与加载过程中各种物理量的发展与变化过程，是这一计算系统的突出特点。更多还原

【Abstract】 It has been well recognized that the interaction of soil and support structures, nonlinearities of soil materials and contact surface between soil and structures and the stability of foundation pit slope are three main issues in the construction and design of deep foundation pit engineering. These issues have not been well solved in engineering practice. Therefore these topics are involved in this thesis. The research work done includes as following:1. The hyperbolic-type nonlinear model and rigid and perfectly-plastic model are usually adopted to simulate the constitutive behavior in tangent direction of contact surface. in fact, however, the hyperbolic-type nonlinear model can not definitely display the plastic flow deformation after shear failure while rigid-perfectly-plastic model can not describe the nonlinear deformation before shear failure. In order to overcome these drawbacks, elastic and elasto-plastic theories are combined together and a nonlinear elasto-perfectly plastic model is developed to simulate nonlinear and inelastic behavior of interaction between soil and structure. In the model, shear deformation before shear failures is computed by the nonlinear model and the plastic deformation after shear debonding is given by the elasto-plastic model. Therefore, the model can comprehensively show the deformation behavior and failure mechanism of the contact surface. On the basis of this constitutive model for contact surface, the contact-zone element with a certain of thickness for numerical simulation of the contact surface between soil and structure is proposed for FEM-based computations. Based on numerical analyses, it is recognized that the contact-zone element with non-zero thickness, instead of no-thickness contact element, should be employed to simulate behavior of soil and structure interaction.2. Two types of nonlinearity occur usually in geotechnical engineering problems, i.e., physical nonlinearity caused by the nonlinear behavior of geo-materials, and geometrical nonlinearity induced by the nonlinear characteristics of interfaces between soil and structure. For such twice nonlinear problems, the elsto-perfactly-plastic model is used for displaying soil nonlinear behavior and the nonlinear elasto-perfectly plastic model developed in this thesis is employed for describing the nonlinear behavior of contact surfaces. Then an effective nonlinear algorithm which combines the incremental procedure and iterative scheme is developed for solving the resulting nonlinear FEM equations. The proposed numerical method is applied to numerical analyses of foundation pit excavation and bracing and slope stability. A number of numerical examples are given to verify the efficiency and validity of the proposed procedure.3. The slope stability analysis based on the elasto-plastic FEM by using shear strength reduction techniques has been commonly accepted and widely used in slope engineering. Based on the computed displacements or generalized shear strain at a certain state of slope in which convergence of iterations of finite element computations cannot be gained, such a state is usually defined as the instable state. At the moment of instability, the variations and distributions of some physical quantities such as plastic strain and stress level are used to assess the initiation and development of failure zone. Therefore, the conventional procedure for defining the instability state by controlling the maximum iterative number for convergence judgment is not appropriate. Moreover, such a convergence criterion that the ratio of unbalanced residual forces to totalexternally-applied loads or the ratio of incremental displacements to the total displacements cannot exceed 10~3 shows a certain degree of man-made randomness. In fact, the distribution of generalized shear strain at any stage before overall failure occur can be displayed based on the computational results of elasto-plastic finite element analyses by using strength reduction technique. While the distribution zone of generaliz更多还原